Fix AssertionError raised from _set_rules_for_policy
Fix AssertionError raised from _set_rules_for_policy

In this function process, once a fw_policy create/update, we should focus
on this fw_policy related resources only, such as its fw_rules. But when add
the relationship into fw_policy, it will query all the related rows with
the rule_ids. This may get the other policy_rule row in
firewallpolicyruleAssociation table. So this patch add the
'firewall_policy_id' into filter, it will get the result owned by the
policy you create/update.

Change-Id: I843bdbe463ec83c752e07cd3e7aa4f52c7038ede
Closes-Bug: #1657358

openstack/neutron-fwaas,openstack/neutron-fwaas